Superheterodyne receiving system



P. D. LOWELL SUPERHETERODYNE RECEIVING SYSTEM Nov. 30, 1937.

Filed July 25, 1933 Patented Nov. 30, 1937 UNITED STATES v 2,100,606 SUPERHETERODYNE RECEIVING SYSTEM Percival D. Lowell, Chevy Chase, Mdgassignor to Radio Corporation of America, New York, N. Y., a corporation of Delaware Application July 25, 1933, Serial No. 682,130

12 Claims. (01. 2 50 20) My invention relates broadly to radio receiving systems and more particularly to an improved circuit arrangement fora superheterodyne type of radio receiver.

5 One of the objects of my invention is to provide a simple and efiicient method of coupling the oscillator with the first detector circuit of a superheterodyne type of radio receiver.

Another object of my invention is to provide 0 an improved method of assembly for superheterodyne types of radio receivers wherein the various elements may be arranged inany manner desired in the design of the receiver, and the oscillator positioned in the most convenient .lo-

cation from a mechanical viewpoint while obtaining the desired degree of coupling between the oscillator and the first detector circuit.

Still another object of my invention is to provide a circuit arrangement for a superheterodyne type of radio receiver including an oscillator and a first detector having means for selectively adlusting the amount of radio frequency energy fed into the first detector from the oscillator to the proper value for the best operation of the first detector. r

A further object of my invention is to provide a circuit arrangement for a superheterodyne type of radio receiver whereby the coupling between the oscillator and the first detector is maintained 0 substantially constant independent of frequency variations thereby obtaining maximum response of the receiver over the wide band of signaling frequencies.

A still further object of my invention is to 35 provide a superheterodyne type of radio receiver employing a screen grid tube as the'first detector and an electron tube oscillator in combination with means for establishing an electron vcoupling between the electron tube oscillator and the first 40 detector. Y e

, Another object of my invention is to provide a circuit arrangement for a superheterodyne type of radio receiver in which the high frequency oscillator is coupled to the first detector of the superheterodyne receiver through a non-inductive resistance. V

A further object of my invention is to provide a superheterodyne type of radio receiving circuit 50 in which the high frequency oscillator is connected with a screen grid type of first detector and in which the relationshipof screen grid potential on the first detector and the plate potential on the oscillator is such that the same source '55 of potential may be employed for energizing both the oscillator plat and the first detector screen rid. V i 1 Other and further objects of my invention re-.

side in a constant coupling system for the oscillator and first detector of a superheterodyne type .5 1

of radio receiver, as set forth more fully in the specification hereinafter following by; reference to the accompanying drawing which diagram-.

matically illustratesa preferred form of my in vention. e 10 My invention is directed particularly to superheterodyne types of radio receiver circuits and provides-a novel, simple and eflicient method of obtaining the desired coupling between the. oscillator and the first detector circuit. The common 1 method now generally used wherein the-two cir-. cuits are directly electromagnetically coupled together is not entirely satisfactory, due mainly to structural positions because the inductance coils of the two circuits must either be positioned ad: 20

jacent to one another or else additional exterior means of magnetic coupling must be' provided. It would be desirable to arrange the oscillator and first detector circuits in a similar manner and symmetrical with the otherelements of the 25 receiver such as the radio frequency and intermediate frequency elements. Heretofore, various types of coupling circuits employing capacity and inductance elements between the oscillator and first detector of the superheterodyne receiver V have been provided but in such systems, the amount of energy, transferred from the oscillator to the first detector has varied with frequency.

My invention provides for an arrangement wherein the various elements of the superheterodyne receiver may be arranged in any manner desired and then the oscillator to first detector coupling inserted afterward and the amountof coupling adjusted to the proper value without disturbing the other-portions of the'receiver-vcir- 40 cuit. The-coupling circuit of my invention provides means for effecting the transfer of a constant amount of energy from the oscillator to the first detector independent of changes in frequency. .The circuit provides means. in a superheterodyne receiver for adjusting the-amount of radio frequency energy transferred by the oscillator to the first detector to the proper valuefor the best operation of the first detector.

In order to clarify my invention, I have omitted the usual radio frequency amplifier normally connected between the antenna circuit I and the first detector 2. The drawing diagrammatically shows a superheterodyne type of receiver circuit including the antenna circuit I, the-first detector 2, the intermediate amplifier 3, the second detector 4, the audio frequency amplifier 5, the audio frequency output circuit 6 and oscillator I. I have illustrated the heater type of tube employed throughout the several stages of the receiver and oscillator and in the first detector, I employ a screen grid type of tube.

Coupling between the oscillator l and first detector 2 is provided by connecting the plate 8 of the oscillator I, through non-inductive resistance 9, to the screen grid ID of the first detector 2. An adjustable tap l 2 is provided on non-inductive resistance 9 for varying the effective value of the resistance between the plate of oscillator 8 and the screen grid IU of first detector 2. The noninductive resistance 9 has a maximum value of the order of 500 ohms, By varying the 'value of the resistance 9, the proper degree of coupling will readily be found. The value ofthe plate voltage used on the plate of .theoscillatoris chosen so as to be the proper voltage for the,

screen grid!!! of the first detector 2, because it will be seen that the plate voltageof the oscillator is also substantially the same as thatof the screen grid of the detector. That is to say,.the oscillator plate potential is obtained from the main plate supplyand the screen grid potential of the first detectoris derivedtherefrom, as determined by the selected value of resistance 9.

The high frequency oscillator .l isso arranged with respect to the first detector 2 that high fre quency. oscillations are impressed upon thefirst detector 2 through the. electron coupling obtained by the connection of the. output of the oscillator circuit through lead l4 extending fromone side of tuned circuit l5 of the oscillator to one side of the circuit constituting the first detector and through the non-inductive resistance 9 to the screen grid Ill. The plate circuit of the oscillator fl extends through inductance 16 which is coupled with the inductance of tuned circuit {5 to the tap l1 on the main source of platepotential .l8 of the radio receiver. The coupling between the high frequency oscillator l and the first detector Z is effected through the electron stream in thefirst detector 2. The amplitude ofthe energy supf plied to the first detector from the oscillator is adjusted by movement of tap l2 along non-induc; tive resistance 9 and at the same time, the potential on screen grid I0 is determined.

I have found the circuit arrangement of my in: vention highly effective inoperation andwhile I have described one of the preferred embodiments of myinvention, I desire that it be understood that modifications may be made and that no limitations upon my invention are intended ether ,than are imposed by the scope of the; appended claims. I H .What I claim as new and desire to secure by Letters Patent of the United States is as follows:

1, In a superheterodyne receiver, an oscillator 'circuit including a plate electrode, a first detector circuit including a screen grid, a resistance connected, directly between, the oscillator plate ,and the screen grid of the first detectorfor pro viding a coupling path between the oscillator and 2. In a superheterodyne. receiver, an oscillator circuit including a plate electrode, a first detector circuit including a screen grid, a conductive connection. from one side of said oscillator circuit to one side of said detector circuit, and a con- .ductive connection between the plate electrode of saidoscillator and thescreen gridelectrode of said first detector.

3. In a superheterodyne receiver, an oscillator circuit including a plate electrode, a first detector circuit including a screen grid, a source of plate potential for said oscillator circuit, a conductive connection from one side of said oscillator circuit to one side of said first detector circuit, and a conductive connection between the plate electrode of said oscillator and the screen grid of saidfirst detector, said last mentioned conductive connection providing a path for high frequency currents and providing means for impressing potential from said source of plate potential to the screen grid of said first detector.

4. In a superheterodyne receiver, an oscillator circuit including a-plate electrode, a first detector circuit including a screen grid, a source of plate potential for said oscillator circuit, a conductive connection from one side of said oscillator circuit to'one side of said first detector circuit, and a conductive connection between the plate electrode of said oscillator and the screen grid of said first detector, said last mentioned conductive connection including anadjustable resistance andprovidinga path for regulating the fiow of high frequency energy from said oscillator eircuit to the said first detector circuit and also, providing a path for impressing bias potential upon, said screen grid from said source'of plate potential. f a

5. In a superheterodyne receiver, an oscillator circuit including aplate electrode, afirst deteca tor circuit including a screen grid, a source of plate potential for said. oscillator circuit, a iconductive connection from one side of said'oscilla} tor circuit to one side of said first detector circuit, and, a conductive, connection between the plate electrode of said oscillator and the screen grid of said first detector, a non-inductive resistance disposed in said last mentioned connec: tion and providing a path for the transfer of high frequency oscillations fromsaid oscillator circuit to the screen grid, of said first detector circuit while simultaneously providing a means for impressing a bias potential on said screen grid electrode of said first detector from said source of plate potential.

6. In a superheterodyne receiver, an oscillator circuit including a plate electrode, a first detector circuit includinga screen grid, a source of plate potential for said oscillator circuit, a conductive connection from one side of said oscillator circuit to one side of said first detector circuit, and a conductive connection between theplatc electrode of said oscillator and the screen grid of said first detector, at non-inductive resistance disposed in said last mentioned connection, and an adjustable tap on said non-inductive resistance for controlling the effective resistance in said last mentioned connection and regulating the amount of high frequency energy supplied by said oscillator to said first detector while controlling the potential impressed upon said screen grid from said source of plate potential.

'7. In a superheterodyne receiver, a high frequency oscillator circuit including a plate electrode and a source of plate potential, a first detector circuit including a screen grid electrode,

8. In a superheterodyne receiver, a high frequency oscillator circuit including a plate electrode and a source of plate potential, a first detector circuit including a screen grid electrode, means for establishing an electronic coupling between said first detector circuit and said high frequency oscillator circuit comprising a conductive connection between one side of said oscillator circuit and said first detector'circuit and a connection between the plate electrode of said high frequency oscillator circuit and .the screen grid of said first detector, and a variable resistance element included in said last mentioned connection for regulating the amount of high frequency energy supplied from said high frequency oscillator to said first detector while controlling the potential impressed upon said screen grid from said source of plate potential.

9. In a superheterodyne receiver, a high frequency oscillator circuit including a plate electrode and a source of plate potential, a first detector circuit including a screen grid. electrode, means for establishing an electronic coupling between said first detector circuit and said high frequency oscillator circuit comprising a conductive connection between one side of said oscillator circuit and said first detector circuit and a connection between the plate electrode of said high frequency oscillator circuit and the screen gridof said first detector, and a non-inductive resistance element included in said last mentioned connection for regulating the amount of high frequency energy supplied from said high frequency oscillator to said first detector while controlling the potential impressed upon said screen grid from said source of plate potential.

10. A radio receiver comprising a plurality of circuits each of which has a space discharge device associated therewith, one of said space discharge devices being connected to act as a local oscillator and another of said space discharge devices being connected to act as a first detector, said first detector including a screen'grid positioned between the control grid and the anode, and direct current paths connected from the anode and the cathode of said local oscillator to said first detector for impressing an alternating I electrodes, a source of signaling energy, an input circuit for said tube connected between one of said grid electrodes and the cathode thereof and including means for coupling said input circuit to said source of signaling energy, an output circuit for said tube including a connection between the anode thereof and the cathode, said connection including a source of plate potential, an oscillator circuit including an" electronic tube having an anode, a cathode and a control electrode, means connecting the last named cathode to thefirst named cathode, means connecting the last named anode to said source of plate potential and a connection between the other grid electrode of the first named tube and the last named anode, said connection including a variable noninductive resistor element, said resistor element providing a coupling path between the oscillator and first detector circuits.

PERCIVAL D. LOWELL. 

